The present invention relates to novel intercalators suitable for electrochemical detection of double strand DNAs(dsDNA), and a process for preparing thereof.
DNA chips have been widely used in gene and molecular biology researches such as the measurement of RNA expression in a large scale, detection of mutant genome DNAs, gene diagnosis, pharmacogenomics and medicine, as they can detect RNAs or DNAs contained in a sample much more efficiently than the conventional Southern blot or Northen blot method.
Generally, DNA chips detect a target DNA, for example, by way of accumulating hundreds of thousands of probe DNA fragments, each having a specified base sequence, on a very small chip surface, contacting the probe DNA fragments with a single strand of the target DNA labeled with a fluorescent material to induce hybridization, and identifying the hybridized DNA by laser irradiation.
However, the above method has the disadvantages that it requires the use of an expensive optical apparatus including a laser scanner and the cost of fluorescent labeling is high. Further, it is difficult to quantitatively determine the amount of the target DNA in a sample from the luminescent intensity.
Accordingly, there have been numerous efforts to solve the above-mentioned problems. For instance, Clinical Microsensors Inc. suggests a method of detecting a DNA by binding a redox-active material, e.q., a transition metal complex on a selected site of a single-stranded probe DNA, bringing a single-stranded target DNA into contact with the resulting probe DNA to induce hybridization, and measuring the change in the electron transporting rate attributable to the hybridization. In addition, Japanese Patent Publication No. 2000-125865 provides a method of detecting a gene of a specimen DNA by allowing a single-stranded sample DNA to interact with a single strand probe DNA immobilized on an electrode surface in the presence of an electrochemically active intercalator, e.g., N-N-bis[[4-(3-ferrocenecarboxaminopropyl)piperazinyl]propyl] naphthalene-1,4,5,8-tetracarboxylic acid, to form a hybridized DNA carrying the intercalator, followed by determining the current which flows through the intercalator.
These methods, however, still exhibit a limited sensitivity for quantitative DNA detection, and thus, there has existed a need to develop an improved intercalator that can be used in a DNA detection method having a higher sensitivity.
Accordingly, it is an object of the present invention to provide a novel intercalator suitable for detection double strand DNAs with a high sensitivity.
It is another object of the present invention to provide a process for preparing the inventive compound.
It is another object of the present invention to provide a novel intermediate used in said process.
In accordance with one aspect of the present invention, there is provided N-[3-[4-(3-ferrocenecarboxamidopropyl)piperazinyl]-propyl]-1,8-naphthalene imide of formula (I): 
In accordance with another aspect of the present invention, there is provided a process for preparing the compound of formula (I) comprising reacting the compound of formula (III) with 1,4-bis(3-aminopropyl)piperazine in an organic solvent to obtain the compound of formula (II), and reacting the compound of formula (II) with 1,8-naphthalic anhydride in an organic solvent in the presence of a base: 
In accordance with still another aspect of the present invention, there is also provided the intermediate compound of formula (II).